HxBP is labeling metalloproteinases <i>in vivo</i>.

<p>Composite confocal micrographs of 72 hpf zebrafish embryos injected anteriorly (*) with 50 µM of trifunctional HxBP probe either with (B) or without (A) competition from unlabeled GM6001. Embryos pre-injected with GM6001 show dramatically attenuated HxBP labeling, requiring the data shown in panel B to be collected using 42% increased gain in order to be detectable. Structures showing strong labeling in HxBP labeled 72 hpf embryos include proliferative myofibrils along the anterior lateral midline (m), maturing myotome boundaries (mb), the horizontal myoseptum (hm), individual migratory mesenchyme cells (mc), and the developing vasculature including the dorsal aorta (da), posterior cardinal vein (pcv) and intersomitic vessels (isv). Asterisk marks the injection site. Scale bar is 500 µM.